R7128 is a prodrug of PSI-6130, an oral cytidine nucleoside analog polymerase inhibitor of HCV that is being developed through Pharmasset’s collaboration with Roche. As noted on 3-Oct, Pharmasset has commenced dosing in a 28-day Phase 1 clinical trial to evaluate R7128 in combination with Pegasys (pegylated interferon) plus Copegus (ribavirin) in treatment-naive patients chronically infected with hepatitis C virus (HCV) genotype 1.